Novel structure of self-powered controllable photodetector based on multiband highly mismatch materials

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Chinese explanation / 中文解读

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Original abstract

Abstract This work demonstrates novel highly tunable multiband photodetectors based on highly mismatched alloys (HMAs), in particular dilute GaAsN. The device features a monolithic anti-parallel structure (Au/n-GaAs (substrate)/p-AlGaAs/n-GaAsN/p-GaAsN/p-AlGaAs/Au) with three stacked p/n junctions, engineered to exploit the unique three active energy bands structure in GaAsN. By varying the nitrogen concentration within the range of 3 to 5% in the GaAsN layers, the energy band positions can be adjusted, enabling precise tuning of the photodetector's spectral response. Under bias, the different p/n junctions in the device are either connected in forward or reverse polarity simultaneously. The operational principles are based on an interband tunneling carrier transport mechanism at the reverse-biased junctions in conjunction with diffusion currents in the forward-biased junctions. We present the design, growth, and characterization of the devices, showing that their photocurrent can be selectively activated across different spectral ranges by adjusting the nitrogen composition in the GaAsN layers. As examples, Device-1 (3% N) exhibits a dual-band response at 500 nm and 800 nm with an EQE of 2.15% at 500 nm and 0.13% at 800 nm, a specific detectivity (D*) of 1.8×10¹⁰ Jones, and response times of 370 μs (rise) and 200 μs (fall), while Device-3 (5% N) shows a single narrow-band response at 940 nm. Importantly, the devices were not optimized for high EQE; rather, the key achievement is the tunable spectral response achieved simply by varying the nitrogen content in the GaAsN layers. This approach establishes a new paradigm for spectrally agile photodetection, moving beyond traditional filter-based or complex tandem structures to a simplified, material-centric tuning strategy.

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